JP2007080561A - Simulation circuit for calculating arc period of fuse - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit capable of accurately simulating fusing time of a fuse built in a device and characteristics in an arc period immediately after a fuse fuses. <P>SOLUTION: This simulation circuit for calculating the arc period of the fuse includes a detector 16 for detecting a current flowing in the fuse built into the device, a first computing part 18 connected with the detector 16 and calculating fuse fusion energy, a second computing part 21 connected with the detector 16 and calculating diffusion energy, a comparing element 25 for comparing results of operations of the first and second computing parts, and an arc computing part 31 for measuring the arcing time during the arc period immediately after the fuse fusion and changes of the current flowing the fuse and the voltage at its ends. When the comparing element 25 detects that the fuse has reached the fusing time, the arc computing part 31 is connected between the device and the detector 16. And changes of the current and the voltage are accurately simulated immediately after the fuse fuses. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a simulation circuit that accurately calculates characteristics in an arc period when a fuse is blown, that is, arc time and voltage-current characteristics that change at that time.

  In a conventional simulation fuse model, a fuse interruption test is actually performed to measure changes in current and voltage, and a change in fuse resistance with time is calculated from changes in current and voltage obtained by measurement. The fuse was modeled as a resistance that changes with time and incorporated into the simulator.

FIG. 3 shows an example of the resistance change of the fuse calculated from the current and voltage waveform that has passed through the fuse. Such data is obtained by experiment. In other words, it is necessary to conduct an experiment each time the rated capacity of the fuse, the composition and structure of the metal change, and obtain data on resistance change when the fuse is blown.
Regarding the calculation of the fusing time, the current flowing through the fuse is calculated using the fuse test circuit of FIG.

ここで、Ｒはヒューズ抵抗を含む回路抵抗、Ｌはケーブルインダクタンス、Ｅは電源電圧である。（１）式をｉ（ｔ）について解くと、（２）式になる。

（２）式を用いることより、ジュール積分値Ｗ１は（３）式で表される。

In FIG. 4, 11 is a DC power source, 12 is a resistor, 13 is an inductance, 27 is a fuse, and 28 is a switch.
There is a method of setting the fusing time when the energy accumulated in the fuse 27, that is, the integrated value of heat reaches the reference energy (allowable energy) for fusing the fuse 27. In particular, in many cases, the resistance of the fuse 27 is constant, and the Joule integral value which is a value obtained by integrating the current flowing through the fuse 27 is often expressed.
First, a Joule integral value W1 which is energy stored in the fuse 27 is obtained. The time when the shorting switch is turned on is t = 0. The current i (t) after t seconds is expressed by equation (1).

Here, R is a circuit resistance including a fuse resistance, L is a cable inductance, and E is a power supply voltage. When equation (1) is solved for i (t), equation (2) is obtained.

By using the equation (2), the Joule integral value W1 is expressed by the equation (3).

On the other hand, the allowable energy value W2 often uses a part of the catalog value provided by the manufacturer. In the case where the fuse 27 used for communication has a current large enough to be interrupted within about 10 ms, the allowable energy value is often constant regardless of the fusing time. Therefore, W2 can be regarded as a constant.
The time t when W1 = W2 is the fusing time. FIG. 5 shows a graph for explaining the fuse blowing time. This graph shows the time change of the Joule integral value obtained by substituting an allowable energy value, a certain inductance value, and a resistance value into the right side of Equation (3). The intersection of the allowable energy value and the calorific integral value obtained by calculation is the fusing time.
The above solution is valid only when the fuse 27 has a large passing current enough to blow within about 10 ms. When the passing current to the fuse 27 is small, that is, when the fusing time is lengthened, the allowable energy value changes with time, and the calculation becomes complicated. Also, whenever the circuit constant changes, the joule integral value and fusing time are derived. Then, it becomes necessary to build a simulation circuit by inputting this value into the fuse switch.
In addition, when the fuse 27 is incorporated in a large-scale power supply system circuit, the interaction between a plurality of circuit elements is strengthened. For this reason, it is impossible to analyze the fuse blow time using the parameters of the simple circuit shown in FIG.

  FIG. 6 shows the difference in current passing through the fuse 27 in the simple circuit (FIG. 4) and the large-scale power feeding system circuit. It can be seen that even if the inductance value and resistance value included in the short circuit are the same, the current increase rate of the large-scale power feeding circuit is small and the current value in the steady state is also small compared to the simple circuit. Therefore, the time for reaching the allowable energy value, that is, the fusing time and the passing current immediately before fusing differ between the simple circuit and the large-scale power feeding system circuit.

  As means for solving such a problem, the present inventor has filed a patent application separately for a fuse fusing time simulation circuit (Japanese Patent Application No. 2005-86013). The circuit includes a detection unit that detects a current flowing through the circuit, a first calculation unit that is connected in series to the detection unit and calculates fuse fusing energy when the detection start switch is ON, and the first calculation unit A second calculation unit that is connected in parallel to calculate the dissipated energy when the detection start switch is ON, a comparison unit that compares the calculation results of the first and second calculation units, and a target device And a fuse switch that simulates the state of the fuse, and when the fluctuation current generated at the time of the incomplete short-circuit is equal to or greater than a threshold value, the detection start switch is turned on and the fluctuation current is equal to or less than the threshold value. In this case, the detection start switch is turned off.

The circuit diagram is shown in FIG. 7 and the operation thereof will be described below.
A DC power supply 11, a resistor 12, an inductance 13, a short-circuit switch 14, and a fuse constitute one device. In the circuit of FIG. 7, the fuse is replaced with a series circuit including a fuse switch 15 and a detection unit 16. Then, the current flowing through the fuse, that is, the replaced fuse switch 15 is measured. In addition, the resistance value and the inductance value of the entire device including the fuse are grouped into one block of the resistor 12 and the inductance 13, respectively.
The first calculation unit 18 includes a calculation unit 19 and an integration unit 20, and the second calculation unit 21 includes a comparison unit 22, a calculation cutoff switch 23, and a calculation unit 24.
Initially, the short-circuit switch 14 is OFF and the fuse switch 15 is ON. When the short-circuit switch 14 is turned on and a current is passed through the circuit, the detection unit 16 detects the current, converts it to a voltage V ₀ and outputs it.

The threshold value for storing energy in the fuse is defined as _Vth . When V ₀ > V _th , it is a fusing mode, and the detection start switch 17 is connected to the first calculation unit 18. At this time, the calculation unit 19 of the first calculation unit 18 squares to obtain the fusing value V _m . Further, assuming that the calculation start time of the calculation unit 19 is 0 second, the integration unit 20 integrates from 0 second to a certain time t ₁ second, and derives the fusing cumulative value V ₁ (t ₁ ). The comparison unit 25 compares the fuse catalog value V ₂ with the fusing cumulative value V ₁ (t ₁ ), and derives an effective cumulative value V ₃ (= V ₂ −V ₁ ) that is the difference between them.
Here, catalog value V ₂ can be easily derived as the I2t by relationship issued by that fusing time with the fusing current of the fuse manufacturer. The value of V ₃ is judged that the blow if it is positive, to continue current detection.

Further, when time passes and V ₃ = 0, the fuse switch 15 is opened (OFF). Therefore, the time when V ₃ = 0 is the fusing time.
When the voltage V ₀ output from the detection unit 16 after turning on the short-circuit switch 14 is equal to or lower than the threshold value V _th (V ₀ ≦ V _th ), the detection start switch 17 is connected to the second calculation unit 21. It connects and becomes the mode which dissipates (releases) the energy stored in the fuse.
In the 2nd calculating part 21, the energy to dissipate is calculated. The comparison unit 22 calculates a difference V _d1 (= V _th −V ₀ ) between the threshold value V _th and the voltage V ₀ output from the detection unit 16. When the difference V _d1 is positive, the calculation cutoff switch 23 is turned on and the value is output to the calculation unit 24. The computing unit 24 calculates the divergence value V _d by squaring the obtained value and multiplying by −1, and outputs it to the integrating unit 20 of the first computing unit.
When V ₀ > V _th , the fusing mode is entered, and the fusing value V _m, which is a positive value, is accumulated by the integrating unit 20 to increase the energy accumulated in the fuse.

On the other hand, when V ₀ ≦ V _th , the dissipation mode is set, and the negative dissipation value V _d is accumulated by the integrator 20 to reduce the energy accumulated in the fuse. The decreasing value is based on the difference between the voltage V ₀ obtained by converting the current passing through the fuse and the threshold value V _th, and the amount of dissipation changes according to the passing current. That is, when the converted voltage is smaller than the threshold value but the difference is small, the amount of dissipation is reduced. Conversely, when the difference is large, the amount of radiation also increases.

By using the fuse fusing time simulation circuit described above, the fusing time of the fuse incorporated in the apparatus can be accurately obtained.
FIG. 8 is a graph comparing the result of simulation using the circuit shown in FIG. 7 and the result of experiment with a fuse incorporated in the apparatus. FIG. 8A is a graph comparing the current passing through the fuse, and FIG. 8B is a graph comparing the voltage across the fuse. Although it agrees well until the fuse blows, it can be understood that simulation cannot be performed during the period from the point where the fuse is blown (melting point) until the fuse passing current becomes 0 and the fuse is blown, that is, during the arc period. . However, there are cases where other communication devices are adversely affected by transient changes in current and voltage immediately after the fuse is blown.
Further, there is a method of simulating the fuse as a variable resistor that changes with time. FIG. 9 shows a circuit diagram in which a fuse is modeled as a variable resistor 26. For example, a DC power supply 11, a short-circuit switch 14, and a fuse are connected to a CFD cable having a cross-sectional area of 38 mm ² and a length of 10 m. Reference numerals 12 and 13 denote resistance and inductance corresponding to the resistance value and inductance value of the CFD cable. The change in the resistance value of the fuse after the short-circuit switch 14 is turned on is measured.

  However, the data of the change in resistance value of the fuse measured in one system cannot be used for the simulation when it is connected to another system as it is.

FIG. 10 shows a graph for explaining it.
FIGS. 10A and 10B show comparison results between simulation values and experimental values when a fuse is connected to a CFD cable having a cross-sectional area of 38 mm ² and a length of 10 m. In this case, the simulation value and the experimental value are in good agreement.
FIGS. 10C and 10D are a comparison with the results of experiments conducted by connecting a fuse to a CFD cable having a cross-sectional area of 325 mm ² and a length of 10 m. The fuse passing current, fusing time, and jumping voltage are greatly different. This is because when the cross-sectional area of the cable changes, the parasitic resistance value and inductance value of the cable change and affect each characteristic.

  The present invention seeks to provide a circuit capable of accurately simulating the characteristics during the arc period immediately after the fuse is blown, as well as the blow time of the fuse incorporated in the apparatus.

  The present invention (1) includes a detection unit that detects a current flowing in a fuse incorporated in a device, a first calculation unit that is connected to the detection unit and calculates fuse fusing energy, and is connected to the detection unit and dissipates. A second calculation unit for calculating energy, a comparison unit for comparing calculation results of the first and second calculation units, an arc time in an arc period immediately after the fuse is blown, a current flowing through the fuse, A simulation circuit for calculating an arc period of a fuse, comprising: an arc calculation unit that calculates a change in voltage at both ends.

  The present invention (2) is the simulation circuit for calculating the arc period of the fuse according to the present invention (1), wherein the arc calculation unit includes a diode.

According to the circuit of the present invention (1), the characteristics in the arc period immediately after the fuse is blown, that is, the arc time and the voltage-current characteristics that change at that time can be accurately simulated together with the fusing time of the fuse incorporated in the apparatus. . By using the results measured with this circuit, for example, if the voltage jump is large during the arc period, overvoltage propagation occurs, affecting other communication devices, and if the fusing time is long, the voltage of the other communication device Since it is conceivable that the decrease period becomes longer and the apparatus is stopped, it is possible to easily design a compensation circuit for protecting other communication apparatuses.
According to the present invention (2), it is possible to accurately simulate the characteristics when the fuse is blown and the voltage at both ends of the fuse is rapidly reduced.

  FIG. 1 shows a simulation circuit for calculating an arc period of a fuse according to an embodiment of the present invention. The simulation circuit for calculating the arc period of the fuse includes a detection unit 16 that detects a current flowing in a fuse incorporated in the apparatus, a first calculation unit 18 that is connected to the detection unit 16 and calculates fuse fusing energy, and a detection unit. 16, the second calculation unit 21 that calculates the dissipated energy, the comparison unit 25 that compares the calculation results of the first and second calculation units 18 and 21, the arc time in the arc period immediately after the fuse is blown, An arc calculation unit 31 that measures changes in the current flowing through the fuse and the voltage across the fuse.

Hereinafter, this embodiment will be described in more detail.
In addition, the same thing as FIG. 7 mentioned above is shown with the same code | symbol. In this circuit, an arc calculation unit 31 is added to the circuit shown in FIG. 7, and the fuse switch 15 is replaced with an arc calculation changeover switch 36.
In the arc calculation unit 31, an arc capacitor 32, an arc resistor 33, and an arc diode 34 are connected in series. In parallel with the arc diode 34, there is connected a resistor 35 that can prevent a simulation error and improve the convergence in numerical calculation.
When simulating the time from when the fuse is incorporated into the apparatus and the apparatus is operated until the fuse is blown, the arc calculation changeover switch 36 is directly connected to the detection section 16 without the arc calculation section 31 being interposed. Then, the short-circuit switch 14 is turned on to start measurement.

The detection unit 16 detects the current flowing through the circuit and converts it into a voltage V ₀ . When the voltage V ₀ is larger than the threshold value, that is, when V ₀ > Vth, the fusing mode is set, and the detection switch 17 is connected to the first arithmetic unit 18. The calculation unit 19 squares the voltage V ₀ to obtain the fusing value V _m , and the integrating unit 20 accumulates the fusing value V _m . When the voltage V ₀ is less than or equal to the threshold value V _th , that is, when V ₀ ≦ V _th , the dissipation mode is set, and the detection switch 17 is connected to the second arithmetic unit 21. The comparison unit 22 calculates a difference V _d1 (= V _th −V ₀ ) between the threshold value V _th and the voltage V ₀ . The computing unit 24 squares the difference V _d1 and multiplies it by −1 to calculate the diffused value V _d and accumulates it in the integrator 20. The value V ₁ accumulated in the comparison unit 25 is compared with the catalog value V _{2 of} the fuse to calculate the effective accumulated value V ₃ (= V ₂ −V ₁ ), and whether or not the fuse fusing time has been reached. To check. The time when V ₃ = 0 is the fusing time of the fuse.

When the comparison unit 25 detects that the fusing time has been reached, the arc calculation changeover switch 36 is switched to the arc calculation unit 31. Then, a change in current after the fuse is blown is simulated.
A fuse is actually attached to the apparatus, and a capacitance value, a resistance value, and the like are calculated in advance from a change in current when the fuse is blown. By configuring the arc calculation unit 31 using the capacitor 32 and the resistor 33 corresponding to these values, it is possible to accurately simulate a change in current after the fuse is blown.
In the circuit shown in FIG. 1, a parallel circuit of an arc diode 34 and a resistor 35 is connected. At the moment when the fuse is cut and no current flows, the voltage across the fuse changes abruptly. This can be simulated by using the diode 34.

FIG. 2 shows a graph in which a fuse is connected to the two types of CFD cables and simulation is performed using the circuit of the present invention. 2 (a) and 2 (b) show a fuse with a cable with a cross-sectional area of 38mm ² and a length of 10m. Figures 2 (c) and 2 (d) show a cross-sectional area of 325mm ² and a cable with a length of 10m with a fuse. Connected. In both cases, the simulated and experimental values are in good agreement.

(Modification of arc calculation unit)
Although the arc calculation unit 31 is shown using an analog circuit, it may be programmed using a CPU or the like and processed digitally. In this case, setting of a capacitance value, a resistance value, etc. is facilitated, and simulation of characteristics of fuses incorporated in various devices can be easily performed.

It is a circuit diagram of the simulation circuit for arc period calculation which is one Example of this invention. It is a graph which shows the result simulated using the simulation circuit for arc period calculation by this invention. It is a graph which shows an example of the resistance change of the fuse computed from the electric current and voltage waveform which passed through the fuse. It is a fuse test circuit diagram for calculating | requiring the conventional fuse fusing time. It is a graph explaining fuse fusing time. It is a graph explaining that the electric current which flows through a fuse differs in two circuits of a simple circuit and a large-scale electric power feeding system. It is a circuit diagram of the fuse blow simulation circuit concerning a prior application. It is a graph which shows the result simulated using the fuse fusing simulation circuit shown in FIG. It is a circuit diagram for demonstrating the method of modeling and modeling a fuse to a variable resistance. It is a graph which shows the result of having modeled a fuse into variable resistance and simulating.

Explanation of symbols

11: DC power supply 12: resistor 13: inductance 14: short circuit switch 15: fuse switch 16: detection unit 17: detection start switch 18: first calculation unit 19: calculation unit 20: integration unit 21: second calculation unit 22 : Comparator 23: Computation cutoff switch 24: Computation unit 25: Comparison unit 26: Variable resistor 27: Fuse 28: Switch 31: Arc computation unit 32: Arc capacitor 33: Arc resistor 34: Arc diode 35: Resistor

Claims (2)

A detection unit that detects a current flowing through a fuse incorporated in the apparatus; a first calculation unit that is connected to the detection unit to calculate fuse fusing energy; and a second unit that is connected to the detection unit and calculates dissipation energy. The calculation unit, the comparison unit that compares the calculation results of the first and second calculation units, the arc time in the arc period immediately after the fuse is blown, the current flowing through the fuse and the change in the voltage across the fuse are calculated. A simulation circuit for calculating an arc period of a fuse. The simulation circuit for calculating an arc period of a fuse according to claim 1, wherein the arc calculation unit includes a diode.

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